The present invention relates in general to detergent compositions and in particular to alkaline earth metal hydrocarbyl phenate compositions.
In the internal combustion engine by-products from the combustion chamber often blow by the piston and admix with the lubricating oil. Many of these by-products form harmful acidic materials within the lubricating oil. Compounds, generally referred to as detergents, are employed to neutralise the acidic materials and disperse sludge within the lubricating oil and also help to keep engine pistons clean from deposits and lacquer. The alkaline earth metal hydrocarbyl phenates are one class of compound which have been used for this purpose. Both "normal" and "overbased" phenates have been employed. Alkaline earth metal hydrocarbyl phenates having BNs (Base Numbers as measured in mg KOH/g by the method of ASTM D2896) of less than about 300, typically 250 or less are well-known in the art. Recently, alkaline earth metal hydrocarbyl phenate compositions having BN's greater than 300, and modified by reaction with carboxylic acid have been made. Thus, our EP-A-271262, for example, discloses an additive concentrate suitable for incorporation into a finished lubricating oil composition, the additive concentrate comprising:
(a) a lubricating oil,
(b) a lubricating oil soluble sulphurised or non-sulphurised alkaline earth metal hydrocarbyl phenate modified by incorporation of from greater than 2 to less than 40% by weight based on the weight of the concentrate of either (i) at least one carboxylic acid having the formula: ##STR2## wherein R is a C.sub.10 to C.sub.24 alkyl or alkenyl group and R.sup.1 is either hydrogen, a C.sub.1 to C.sub.4 alkyl group or a --CH.sub.2 -COOH group, or an anhydride, acid chloride or ester thereof or (ii) a di- or polycarboxylic acid containing from 36 to 100 carbon atoms or an anhydride, acid chloride or ester thereof, the concentrate having a BN greater than 300.